Conventionally, a variety of compressors have been proposed for compressing a compressed medium such as refrigerant in a refrigeration machine, and among those, single screw compressors are known for having small vibration and noise and high reliability.
As described in JP-A No. 2002-202080, there is a single screw compressor that is equipped with a cylindrical screw rotor that has plural helical grooves in its outer peripheral surface, at least one gate rotor that rotates while meshing with the screw rotor, and a casing that houses the screw rotor. A compressed medium such as refrigerant is delivered to the helical grooves in the screw rotor rotating inside the casing, is compressed inside a space enclosed by the helical grooves, teeth of the gate rotor and the casing, and is discharged from a discharge port in the casing.
Further, as described in U.S. Pat. RE 30,400, there is a single screw compressor that is equipped with a screw rotor that has a tapered shape or a reversely tapered shape where its outer diameter changes from an intake side toward a discharge side and a pinion that rotates while meshing with helical grooves in the screw rotor. In this single screw compressor described in U.S. Pat. RE 30,400 also, a compressed medium such as refrigerant is delivered to the helical grooves in the screw rotor rotating inside the casing, is compressed inside a space enclosed by the helical grooves, teeth of the pinion and the casing, and is discharged from a discharge port in the casing.